The Legionella risks specific to food and drink manufacturing live in process water, not the welfare taps: pasteuriser cooling and spray circuits, high-pressure wash-down, refrigeration cooling towers and brewery wort coolers all hold warm water and throw it into the air as breathable mist [5].

If you have already assessed the HVAC plant and the welfare block, you have done the part that both generic industrial and front-of-house catering guidance cover. The water this article is about is the water that exists to make, clean and move product — and it is exactly the water those two guides walk past. Heavy-industry advice such as Legionella prevention in industrial facilities tends to assume a cooling-tower-and-process-cooling site; catering advice such as Legionella in restaurants, pubs and commercial kitchens stops at the kitchen tap and the ice machine. A pasteuriser tunnel sits in the gap between them.

Two water systems, two different questions

The clearest way to frame a manufacturing site is to split its water in two.

One stream is product and ingredient water — the water that ends up in or on the food. That is the territory of your food-safety system, HACCP and FSA-aligned controls, and it is governed by potability and contamination questions. The other stream is non-product water: the recirculated spray on a pasteuriser, the cooling water in a heat exchanger, the wash-down hose, the condenser loop. None of it touches the product, so a food-safety audit rarely looks hard at it — yet it is the stream that warms up, recirculates and aerosolises, which is the precise recipe for Legionella exposure [2][4].

Process water Legionella control is therefore a parallel assessment, not a sub-clause of food safety. The sector-specific risk assessment that ties it together is the one described in BS 8580-1 [6], and each asset then maps to the right part of HSG274: cooling water to Part 1, hot and cold water to Part 2, and the “other” aerosol-generating systems — sprays, water baths, humidifiers — to Part 3 [3].

Pasteurisers: the warm circuit nobody flushes

The asset most sites have never assessed for Legionella is the pasteuriser, and the reason is a misunderstanding. People see “pasteuriser” and think heat, kill step, sterile — so they assume it cannot be a bacterial source.

Look at where the water actually is. In a tunnel pasteuriser, sealed cans or bottles ride through heating and cooling zones while recirculated water is sprayed over them from spray bars. The cooling stages, by design, move that recirculated spray water down through the tepid band in which Legionella multiplies — broadly the 20-45C range HSE associates with proliferation [4] — and the machine throws it as a fine aerosol across an open deck where operators stand. Warm recirculated water plus deliberate spray onto people is the textbook definition of an “other risk system” under HSG274 Part 3 [3]. Plate (HTST) pasteurisers are more enclosed, but they still run cooling and regeneration water circuits that can sit warm and need assessing on the water side, not just the product side.

The pasteuriser Legionella risk is real precisely because the product getting hot tells you nothing about the spray water that cools it. Treat each pasteuriser cooling and spray circuit as an aerosol source on the asset register, and confirm who owns its water-side assessment.

Wash-down and spray cleaning

End-of-shift cleaning is where a food factory generates its densest aerosol clouds. High-pressure hoses, drop hoses, retractable reels and foam lances atomise water across the whole production hall.

Two things make wash-down water aerosol worth assessing. First, the cleaning supply is often warm, drawn from a heated ring main to lift fats and soils — warm enough to support growth if it stagnates. Second, hoses and lances stand full of water between shifts and over weekends, so the line itself becomes a short dead leg that the next blast of spray empties straight into the air people breathe. Manage the hot and cold supply to these stations under HSG274 Part 2, flush hoses that sit unused, and keep the supply temperature out of the growth range [3][4]. Where cleaning standards allow, directed nozzles and lower working pressures cut the aerosol without cutting the clean.

Process cooling and refrigeration

The highest-consequence aerosol source on most beverage and chilled-food sites is the refrigeration plant’s heat rejection. Cooling towers and evaporative condensers serving chillers and cold stores hold large volumes of warm recirculating water and are built to release drift — covered squarely by HSG274 Part 1 [3]. These also carry a legal notification duty: cooling towers and evaporative condensers must be notified to the local authority [7]. The full control regime — water treatment, drift eliminators, cleaning and monitoring — is set out in Cooling towers and evaporative condensers: high-risk systems. Closed-circuit and adiabatic coolers are lower-risk but not automatically out of scope; assess any point where they release spray.

Humidification used to stop product drying in chilled rooms belongs in the same bracket. If it makes a mist, it earns an assessment, on the same logic as Misting systems and humidifiers: Legionella in unexpected places.

Brewery and beverage lines: the cold side of a hot process

Brewery water hygiene follows the same rule — assess the water that cools the product, not the product itself. After the boil, hot wort is chilled fast through a paraflow or plate heat exchanger; the wort side runs near-sterile, but the cooling-water side, and any tower or chilled loop feeding it, is the Legionella concern. Add to that the bottle and can tunnel pasteurisers on packaged beer, keg and cask washing with hot water and steam, and cellar cooling. Soft-drink and juice plants repeat the pattern in carbonation cooling and syrup-room services. Wherever recirculated water cools a hot product, the water side belongs in the survey.

A field checklist for process-water aerosol sources

Use this on a plant walk and record each line — the dated evidence is the point, not the tick. It is deliberately about food and beverage water safety beyond the welfare block.

Pasteurisers and warm process circuits

  • List every pasteuriser cooling and spray circuit on the asset register as an aerosol source, not just a food-safety machine.
  • Confirm the water-side risk assessment covers recirculated spray and cooling water, not only product temperatures.
  • Check spray-zone water for temperature, biofilm and debris on the schedule your assessment sets; log it.

Wash-down and spray cleaning

  • Identify hose stations, drop hoses and foam lines; flush any that stand full between shifts.
  • Keep the wash-down supply temperature out of the growth range.
  • Reduce avoidable aerosol with directed nozzles and lower pressures where cleaning standards allow.

Process cooling and refrigeration

  • Confirm cooling towers and evaporative condensers are notified to the local authority and run the Part 1 regime.
  • Assess closed-circuit, adiabatic and humidification kit for any spray release.

Brewery and beverage lines

  • Assess the cooling-water side of wort coolers and any tower or chilled loop feeding them.
  • Include keg/cask wash, cellar cooling and packaged-product pasteurisers.

Across the system

  • Keep one asset list that separates product/ingredient water from aerosol-generating non-product water.
  • Set sentinel points and control temperatures for the hot and cold supply under Part 2.
  • Reassess after any line change, new pasteuriser, or seasonal shutdown.

This is general guidance, not a substitute for a site-specific assessment by a competent person, and nothing here is legal, medical or engineering-design advice. Your own risk assessment sets the temperatures, frequencies and priorities for your plant, and where this article touches food-safety regimes you should confirm the detail with your food-safety lead and the relevant FSA and industry guidance.

Common questions

Does our HACCP plan already cover Legionella in process water?

Not the part that matters here. HACCP and food-safety systems concentrate on the product and on ingredient-water potability. Legionella exposure comes from non-product water that warms and aerosolises — pasteuriser spray, cooling loops, wash-down — which a food-safety audit rarely assesses. Run it as a parallel assessment under BS 8580-1 [1][6].

Is a pasteuriser really a Legionella risk if the product gets so hot?

The product reaching kill temperature tells you nothing about the spray water that cools it. Tunnel and plate pasteurisers recirculate cooling water through the warm range where Legionella grows and, in tunnels, spray it as aerosol over the deck. That water side is what you assess [3][4].

Do we have to notify our cooling towers and evaporative condensers?

Yes. Cooling towers and evaporative condensers must be notified to the local authority, and they carry the Part 1 control regime for treatment, cleaning and monitoring [3][7].

The next step

Walk the production hall once with the asset register and mark every point that makes warm spray and never appears on a food-safety form: each pasteuriser deck, every wash-down station, the condenser loop on the roof. That single list of non-product aerosol sources is your starting scope — hand it to your competent assessor before the next BS 8580-1 review so the process water gets assessed alongside the taps it has always been hiding behind.

Sources

[1] HSE, “Legionnaires’ disease - what you must do”. https://www.hse.gov.uk/legionnaires/what-you-must-do/index.htm [2] HSE, “Systems most likely to create legionella risk”. https://www.hse.gov.uk/legionnaires/risk-systems.htm [3] HSE, “Legionnaires’ disease: Technical guidance (HSG274)”. https://www.hse.gov.uk/pubns/books/hsg274.htm [4] HSE, “Hot and cold water systems”. https://www.hse.gov.uk/legionnaires/hot-and-cold.htm [5] CDC, “How Legionella Spreads”. https://www.cdc.gov/legionella/causes/index.html [6] BSI, “BS 8580-1:2019 - Risk assessments for Legionella control. Code of practice”. https://knowledge.bsigroup.com/products/water-quality-risk-assessments-for-legionella-control-code-of-practice-1 [7] HSE, “Other duties: RIDDOR and notification of cooling towers or evaporative condensers”. https://www.hse.gov.uk/legionnaires/what-you-must-do/duties.htm